August 12, 1920] 



NATURE 



753 



Perry will probably be chiefly remembered by 

 eng^ineers as the man who broke throug'h the 

 formal defences of mathematics and taught them 

 mathematics throug'h what they knew of 

 machinery. His book on " Practical Mathe- 

 matics," orig-inating- in his Finsbury course, has 

 been translated into many languages, and many 

 generations in many lands will therefore benefit 

 from Perry's determination to teach his own 

 students the fundamental truths of mathematics 

 so well that they could use their knowledge as 

 easily as they could use their mother tongue. 



Perry continued his work as professor of mathe- 

 matics and mechanics at the Royal College of 

 Science, leaving Finsbury in 1896. In those days 

 the professors at the Finsbury Technical College 

 were expected to run an arduous day course, and 

 in addition an evening course as well. His relief 

 at the escape from this double duty was great. 

 In more recent years he guided the fortunes of 

 the British Association for the Advancement of 

 Science as its general treasurer. Perry has done 

 a great work, and his work will live after him. 



W. E. D. 



Pkok. Augusto Righi, For. Mem. R.S. 



Prof. Augusto Righi, who died suddenly on 

 June 8 at seventy years of age, is said to have 

 been appointed assistant to the professor of 

 physics in the University of Bologna — his native 

 city — at the age of twenty-one. In 1877 he was 

 Libero Docente, and in 1880 was appointed 

 ordinary professor at Padua, whence after a few 

 years he returned to Bologna as head of the 

 physics department. 



Righi was a skilled experimenter and an indus- 

 trious worker. His original investigations lay 

 chiefly in the domain of electricity, magnetism, 

 and light. One of his discoveries was the varia- 

 tion of the resistance of bismuth in a magnetic 

 field, a phenomenon on which an instrument for 

 measuring the intensity of a field has been based. 

 He was led to this discovery by an examination of 

 the Hall effect in difi"erent metals in the year 1883. 

 His results were published in the Journal de 

 Physique (2), 1883, p. 512, and in the Comptes 

 rendus, vol. xcvii., p. 672, as well as in Italian; 

 most fully in Bologna Acad. Sci. Mem., vol. v., 

 1^83, pp. 103-26. An abstract was given in 

 Nature, vol. xxx., p. 569. 



Righi 's earliest papers appeared in 1873, and 

 dealt with a variety of topics, many of them con- 

 nected with electrostatic problems and voltaic 

 electricity. One of the subjects on which at one time 

 he laid stress was the dilatation of the glass or 

 quartz of a Leyden jar, and of insulators in 

 general, under electric stress — what he called 

 "galvanic dilatation": see, for instance, 

 Comptes rendus, vol. Ixxxviii., 1879, p. 1262. 

 He also examined the changes of length 

 due to magnetisation, and discussed the 

 phenomena of permanent steel magnets. 

 About 1880 Righi began a long series of re- 

 searches on electric discharge in vacuo and in air, 

 NO. 2650, VOL. 105] 



and pursued the subject in various forms to the 

 end of his life. He was much interested in photo- 

 electric effects, and contributed some new facts to 

 the discharge of electrified bodies by ultra-violet 

 light. He failed to discover electrons, but he 

 knew that carriers of negative electricity were 

 liberated, and took steps to observe their tra- 

 jectory in a magnetic field, thus exhibiting the 

 phenomenon as a variety of cathode rays. He 

 also found that the discharge could be stopped 

 by an electric charge of inverse sign, constant 

 in density for a given metal. 



Righi was keenly interested in the work of 

 Hertz, and corresponded with the present writer 

 on the subject of electric waves. A special form 

 of Hertz oscillator, known as Righi 's pattern, con- 

 sisting of a couple of spheres with adjacent faces 

 immersed in oil and charged at the back from 

 two other spheres, was used by some people, and 

 is depicted as a form appropriate to wireless tele- 

 graphy in Mr. Marconi's first patent, though the 

 connection of the outer spheres to an ele- 

 vated plate and to ground respectively — a 

 plan efficiently introduced by Mr. Marconi 

 for practical purposes — really converted the 

 spherical oscillator into nothing but a series of 

 spark gaps. It is understood that Mr. Marconi 

 had visited Righi 's laboratory and seen his ex- 

 periments on Hertzian waves, but was not one of 

 his students. Righi, in his correspondence, fre- 

 quently expressed surprise at the novelty attri- 

 buted to the invention in its very early days by 

 Sir William Preece and other English officials. 



In the Memoirs of the Academy of Sciences of 

 the Institute of Bologna, Righi expounded many 

 of the new discoveries as they were being made 

 in physics — among- others an excellent and semi- 

 mathematical exposition of the Zeeman pheno- 

 menon (see vol. viii., ser. 5, pp. 59-90, December, 

 1899). He also wrote on the equations of Hertz 

 and their solution, in vol. ix. of the Memoirs of 

 the same Academy, pp. 3-28 (February, 1901); 

 and, again, on the electromagnetic mass of elec- 

 trons in vol. iii., ser. 6, pp. 71-84 (February, 

 1906). These papers show that though chiefly 

 an experimental physicist, he had a sound grasp 

 of general theory, and must have had considerable 

 influence in making known the work of British 

 and other physicists to his countrymen. A memoir 

 on the theory of relativity w'as contributed by 

 Righi to the Institute of Bologna so recently as 

 April 18 last (vol. vii., ser. 7, pp. 70-82). 



An experimental paper of Righi 's on the pos- 

 sible existence of magnetic rays, dated May 17, 

 1908, vol. v., ser. 6, of the same Memoirs, 

 pp. 95-150, deserves mention, because of the 

 cathode ray inquiry there described and the 

 speculation based upon it. The subject is con- 

 tinued in vol. vi., pp. 45-64, and in vol. x., 

 pp. 79-103, also in vol. i., ser. 7, pp. 3-36, where 

 results are described for many different gases. 

 It is taken up again, after a discussion of the 

 paths of electrons in magnetic fields, in vol. ii., 

 ser. 7, pp. 11-41. 



Righi descril>es further experiments in vol. iii., 



